Radical scavenging and antioxidant activity of tannic acid

Tannic acid, a naturally occurring plant polyphenol, is composed of a central glucose molecule derivatized at its hydroxyl groups with one or more galloyl residues. In the present paper, we examines the in vitro radical scavenging and antioxidant capacity of tannic acid by using different in vitro analytical methodologies such as 1,1-diphenyl-2-picryl-hydrazyl free radical (DPPH) scavenging, 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) radical scavenging activity, total antioxidant activity determination by ferric thiocyanate, total reducing ability determination using by Fe³⁺–Fe²⁺ transformation method, superoxide anion radical scavenging by riboflavin–methionine-illuminate system, hydrogen peroxide scavenging and ferrous ions (Fe²⁺) chelating activities. Also, butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), α-tocopherol and trolox, a water-soluble analogue of tocopherol, were used as the reference antioxidant radical scavenger compounds.Tannic acid inhibited 97.7% lipid peroxidation of linoleic acid emulsion at 15 μg/mL concentration. On the other hand, the above mentioned standard antioxidants indicated an inhibition of 92.2%, 99.6%, 84.6% and 95.6% on peroxidation of linoleic acid emulsion at 45 μg/mL concentration, respectively. In addition, tannic acid had an effective DPPH scavenging, ABTS⁺ radical scavenging, superoxide anion radical scavenging, hydrogen peroxide scavenging, Fe³⁺ reducing power and metal chelating on ferrous ions activities. Also, those various antioxidant activities were compared to BHA, BHT, α-tocopherol and trolox as references antioxidant compounds. The present study shows that tannic acid is the effective natural antioxidant component that can be used as food preservative agents or nutraceuticals.     

Phenolic compounds and antioxidant activity of olive leaf extracts

The total phenolic content and antioxidant activities of olive leaf extracts were determined. Plant material was extracted with methanol and fractionated with solvents of increasing polarity, giving certain extracts. The qualitative changes in the composition of the extracts were determined after the storage of leaves for 22?h at 37°C, before the extraction. Total polyphenol contents in extracts were determined by the Folin-Ciocalteu procedure. They were also analysed by liquid chromatography-mass spectrometry. Their antioxidant activities were evaluated using the diphenyl picrylhydrazyl method and the β-carotene linoleate model assay. Moreover, the effects of different crude olive leaf extracts on the oxidative stability of sunflower oil at 40°C and sunflower oil-in-water emulsions (10% o/w) at 37°C, at a final concentration of crude extract 200?mg?kg(-1) oil, were tested and compared with butylated hydroxyl toluene.     

Radical scavenging and catalytic activity of metal-phenolic complexes

A series of metal-ligand complexes were prepared by the reaction of various metal ions, namely, Cu(II), Mn(II), or Fe(II) with phenolic derivatives of [catechol, chlorogenic acid (CGA), n-propyl gallate (nPG), 3-hydroxy anthranilic acid, resveratrol, and rutin] and characterized by UV-vis spectroscopy. The metal/ligand complexing ratio and complexation constants have been determined. The complexes were probed for their reactivity toward various free radicals (e aq-, CO2*-, and O2*-). Pulse radiolysis studies showed that the one-electron reduction of metal/phenol complexes by CO2*- radicals was metal-centered, and this was confirmed by the formation of an initial adduct with CO2*- radicals. Rate constants for the scavenging of superoxide anions with metal complexes ranged between 10(7)-10(9) dm3 mol(-1) s(-1) and those for the reaction of e aq- with the metal complexes were in the range of (1-5) x 10(9) dm3 mol(-1) s(-1), depending on the pH of the solution. Cyclic and differential pulse voltammetric studies showed that the reduction potential of the complexes are found to range between -0.022 to 0.45 V vs normal hydrogen electrode.     

Rosehip extraction: Process optimization and antioxidant capacity of extracts

This article examines the extraction of rosehip to study the recovery of a number of compounds with antioxidant properties (polyphenols, flavonoids, and β-carotene). Two varieties of rosehip, cultivated and wild are used as raw material. A detailed study of the process kinetics at different operating conditions is carried out in order to determine appropriate processing parameters, which results in extracts with higher content of target compounds and higher antioxidant capacity. Data on the concentration of active components in the different parts of the fruit (skin, seeds, and pappi) are also obtained, which gives information about their distribution within the fruit. The comparison of wild and cultivated varieties demonstrates the better quality of the cultivated one. The results are useful for production of improved and enriched rosehip extracts with higher content of antioxidant substances that have proven beneficial effects on the human health.      

Chemical and biological activity of leaf extracts of Chromolaena leivensis

The flavonoids 3,5-dihydroxy-7-methoxy-flavanone, 3,5-dihydroxy-7-methoxyflavone and 3,5,7-trihydroxy-6-methoxyflavone were isolated from the leaves of C. leivensis. Preliminary observations in K562 cells (human erythroleukemia) using the trypan blue test, showed a 90% viability at a concentration of 100 microg/mL; however, further testing of the flavonoids at concentrations of 25, 50 and 100 microg/mL showed toxicity affecting the morphology of human erythroleukemia cells (K562) and human melanoma cells (A375). Induction of apoptosis was produced by 3,5-dihydroxy-7-methoxyflavone at 72 hours after treatment with arrest in the G2 / M phase of the cell cycle. The A375 cells treated with 50 microg/mL of 3,5-dihydroxy-7-methoxy-flavanone for 24, 48 and 72 hours, display effects on the behavior of the cell cycle. The flavonoid 3,5-dihydroxy-7-methoxyflavone has activity on the mitochondrial membrane at concentrations of 25, 50 and 100 microg/mL, at time intervals of 8 to 12 hours. The flavonoids 3,5-dihydroxy-7-methoxy-flavanone and 3,5-dihydroxy-7-methoxyflavone at a concentration of 25 microg/mL increased the expression of costimulatory molecules corresponding to the phenotype presented by mature dendritic cells with differentiation markers CD40, CD83, CD86 and HLA-DR. The two flavonoids at concentrations between 0.39 and 100 microg/mL slightly increased the proliferation of peripheral blood mononuclear cells in the presence and in the absence of phytohemagglutinin. These flavonoids at concentrations of 50 and 100 microg/mL slightly increased the proliferation of fibroblasts.     

Improving antioxidant scavenging effect of fruit peel waste extracts and their applicability in biodiesel stability enhancement

The increasing popularity of fruit peel extracts as effective sources of natural antioxidants is primarily attributed to their affordability, easy availability, and high phenolic contents that readily dissolve in solutions. However, most natural antioxidants demonstrate a lesser free radical scavenging effect when applied in mono blends compared to their synthetic counterparts. To address this problem, this work aims to improve the antioxidant capacities of palm fruit, banana, and mango peel liquid extracts recovered using supercritical fluid extraction (SFE). Firstly, a reverse-phase high-performance liquid chromatography (RP-HPLC) was used to isolate three (3) target bioactive compounds from the extracts, whose estimated quantities ranged between 1.2983–4.6841, 1.1469–3.6987, and 0.0254–0.0489 mg/g for quercetin, beta-carotene, and gallic acid respectively. Subsequently, blends of the recovered extracts were formulated in mono, binary, and ternary dosage ratios (S.₁–S.₁₀) to assess their free radical scavenging efficiency (RSE) in terms of inhibitory concentration at 50% (IC₅₀) using a 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, total phenolic content (TPC), total flavonoid content (TFC), and total carotenoid content (TCC). Based on the results obtained, the highest RSE was exhibited by the ternary blend (S.₉), with an IC₅₀ value of 76.21 ± 032 µg/mL and a TPC value of 242.38 ± 0.26 mg gallic acid equivalent (GAE/g). The fastest kinetics for the extracts’ reaction with DPPH corresponding to a rate constant (K) of 1.2351 M^−1.min⁻¹ and activation energy ($E_a)$ of 0.55 KJ/mol were presented by the same sample blend (S.₉), indicating the ease of hydrogen atom release for radical scavenging. Finally, the peel extracts demonstrate an improved antioxidative performance by prolonging the biodiesel’s induction period of the extracts-blended samples as obtained from Rancimat analysis.     

竹叶提取物的抗氧化活性研究

一般认为黄酮是竹叶提取物中抗氧化作用的有效成分,黄酮含量越高,抗氧化能力越强[1-3]。本实验对不同溶媒竹叶提取物的抗氧化能力做了比较研究,发现抗氧化作用与黄酮含量并不完全成正比关系;并通过进一步的定性实验,证明黄酮并不是竹叶提取物中的唯一的抗氧化有效成分,还有其它     

Radical scavenging properties of nicotinamide and its metabolites

By means of pulse radiolysis the reactivity of nicotinamide, its metabolites and selected pyridinium salts towards reactive oxygen species was tested and compared with the pharmacological efficacy of this group of compounds. It was found that pyridinium salts are poor radical scavengers but the positive charge distribution enhances their interactions with immobilized heparin. Thus, superior pharmacological efficacy of 1-methylnicotinamide may be related to its ability to interact with biological tissues rather than to its direct anti-oxidant properties.     

Hydroxycinnamic acid clustered by a calixarene platform: radical scavenging and antioxidant activity

Novel hydroxycinnamic acid-calix[4]arene hybrids 4 and 5 were synthesized. Their radical scavenging and antioxidant activities were determined by using DPPH radical and AIBN-induced linoleic acid peroxidation test, respectively. Preliminary studies showed that compounds 4 and 5 possess enhanced activity with respect to the corresponding hydroxycinnamic acid and phenetidine derivative. Kinetic solvent effects were taken in account to understand the different antioxidative behaviour of the synthesized compounds.     

A theoretical study on the antioxidant activity of Uralenol and Neouralenol scavenging two radicals

Uralenol and neouralenol are two typical licorice root extracts that presents multiple reactive hydroxyl groups, which are considered as good free radical scavengers. A theoretical study on the primary antioxidant activity of uralenol and neouralenol toward hydroxyl and hydroperoxyl radicals has been carried out using the density functional theory (DFT). A total of 10 reaction pathways of uralenol and neouralenol scavenging two radicals in gas phase and in water phase have been tracked. Neouralenol was found to be a better hydroxyl and hydroperoxyl scavenger than uralenol. In vivo, the more reactive sites in uralenol are U5 and U’1, respectively, for scavenging ·OH and ·OOH; and the more reactive sites in neouralenol are N4 and N’5 for scavenging ·OH and ·OOH, respectively.     

Phenolic composition,antioxidant and antinociceptive activities of Syringa vulgaris L. bark and leaf extracts

Metabolite profile, antioxidant and antinociceptive activities of Syringa vulgaris bark and leaf methanolic extracts were investigated. By means of HPLC-DAD-ESI-TOF and HPLC-DAD-ESI-MS/MS, a total of 33 phenolics were identified, including 15 secoiridoids, 6 phenylpropanoids, 3 flavonoids, 3 lignans and 6 low molecular weight phenols. Validated quantitative analysis show that syringin (2.52%) and rutin (1.13%) are the main phenolic compounds in bark and leaf, respectively. Notable radical scavenging and antinociceptive activities of the bark and leaf extracts were confirmed by in vitro DPPH^● and ABTS^●+ assays and by in vivo hot-plate method in mice, respectively. Our results could lay the scientific basic of future clinical perspectives of lilac bark and leaf.     

Analysis of the antioxidant activity of an indole library: cyclic voltammetry versus ROS scavenging activity

The electrochemical behavior of an indole library of compounds, including several tryptophan and tryptamine derivatives previously demonstrated to be active against several reactive oxygen species (ROS), was investigated. For this purpose, a voltammetry study was undertaken and the oxidation potential was correlated to the scavenging activity reported for the studied indoles. All the compounds showed an oxidation potential peak lower than that observed for indole (Epox = 1.035 V), but higher than that described for the antioxidant melatonin (Epox = 0.715 V). The electrochemical behavior showed a high correlation with the scavenging activity of peroxyl radical, for selected compounds.     

Antimicrobial and antioxidant phytochemicals in leaf extracts of Bergenia ligulata: a Himalayan herb of medicinal value

Phenolic and flavonoid contents in leaf extracts of Bergenialigulata have been analysed for their contribution in antimicrobial and antioxidant activities. The extracts were prepared in three solvents (separately) following maceration and soxhelt methods. The antimicrobial activity was tested using disc diffusion assay against a range of microorganisms along with the determination of minimum inhibitory concentration (MIC), while the antioxidant activity was tested following DPPH assay. Leaf extracts exhibited antimicrobial activity against all the three groups of microorganisms; results coincided with respective MIC. In general, the methanol extracts prepared through maceration favoured the determination of antimicrobial and antioxidant activities. Maximum values for phenolic and flavonoid contents were obtained in macerated methanol and ethyl acetate extracts, respectively. The statistical correlations exhibited the extent of the contribution of phenolic and flavonoid contents in antimicrobial and antioxidant activities and also indicated the involvement of other plant metabolites.     

甘松不同溶剂提取物的抗氧化活性研究

采用DPPH、ABTS、羟自由基、超氧阴离子和还原力五种体外抗氧化测定方法对甘松95%乙醇提取物以及石油醚萃取物,乙酸乙酯萃取物,正丁醇萃取物和水萃取物等4个不同极性部位的抗氧化活性进行评价,同时分析抗氧化活性与其总多酚和总黄酮含量的相关性。研究结果表明,除水和石油醚萃取物外,甘松其他3个萃取物均表现出一定的抗氧化活性,且与总多酚和总黄酮含量呈显著相关。其中,乙酸乙酯萃取物中总黄酮和总多酚含量最高,分别为(157.22±1.89)mg·g-1和(99.43±1.23)mg·g-1,其清除DPPH、ABTS、超氧阴离子和羟自由基的IC50分别为(0.20±0.02)mg·mL-1、(0.15±0.01)mg·mL-1、(0.29±0.02)mg·mL-1和(0.35±0.02)mg·mL-1。甘松的乙酸乙酯萃取物具有显著的抗氧化活性,可以成为天然抗氧化活性化合物的良好来源。     

Structure of dihydrochalcones and related derivatives and their scavenging and antioxidant activity against oxygen and nitrogen radical species

Quantum mechanical calculations at B3LYP/6-31G** level of theory were employed to obtain energy (E), ionization potential (IP), bond dissociation enthalpy (O-H BDE) and stabilization energies (DE(iso)) in order to infer the scavenging activity of dihydrochalcones (DHC) and structurally related compounds. Spin density calculations were also performed for the proposed antioxidant activity mechanism of 2,4,6-trihydroxyacetophenone (2,4,6-THA). The unpaired electron formed by the hydrogen abstraction from the phenolic hydroxyl group of 2,4,6-THA is localized on the phenolic oxygen at 2, 6, and 4 positions, the C? and C? carbon atoms at ortho positions, and the C? carbon atom at para position. The lowest phenolic oxygen contribution corresponded to the highest scavenging activity value. It was found that antioxidant activity depends on the presence of a hydroxyl at the C2 and C4 positions and that there is a correlation between IP and O-H BDE and peroxynitrite scavenging activity and lipid peroxidation. These results identified the pharmacophore group for DHC.     

Phenolic composition, antioxidant capacity and antibacterial activity of selected Irish Brassica vegetables

Vegetables belonging to the Brassicaceae family are rich in polyphenols, flavonoids and glucosinolates, and their hydrolysis products, which may have antibacterial, antioxidant and anticancer properties. In the present study, phenolic composition, antibacterial activity and antioxidant capacity of selected Brassica vegetables, including York cabbage, Brussels sprouts, broccoli and white cabbage were evaluated after extraction with aqueous methanol. Results obtained showed that York cabbage extract had the highest total phenolic content, which was 33.5, followed by 23.6, 20.4 and 18.4 mg GAE/g of dried weight (dw) of the extracts for broccoli, Brussels sprouts and white cabbage, respectively. All the vegetable extracts had high flavonoid contents in the order of 21.7, 17.5, 15.4 and 8.75 mg QE/g of extract (dw) for York cabbage, broccoli, Brussels sprouts and white cabbage, respectively. HPLC-DAD analysis showed that different vegetables contain a mixture of distinct groups of phenolic compounds. All the extracts studied showed a rapid and concentration dependent antioxidant capacity in diverse antioxidant systems. The antibacterial activity was determined against Gram-positive and Gram-negative bacteria. York cabbage extract exhibited significantly higher antibacterial activity against Listeria monocytogenes (100%) and Salmonella abony (94.3%), being the most susceptible at a concentration of 2.8%, whereas broccoli, Brussels sprouts and white cabbage had moderate to weak activity against all the test organisms. Good correlation (r2 0.97) was found between total phenolic content obtained by spectrophotometric analysis and the sum of the individual polyphenols monitored by HPLC-DAD.     

Antibacterial,antioxidant and photocatalytic activity of novel Rubus ellipticus leaf mediated silver nanoparticles

Nanotechnology is an emerging field of science that has significant applications in applied sciences. In this study, silver nanoparticles (SNPs) were synthesized utilizing the leaf filtrate of Rubus ellipticus. SNPs were characterized using UV–visible spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction patterns to determine their morphology and chemical composition. The surface plasmon resonance of SNPs revealed a peak at 415 nm. The synthesized SNPs were mainly spherical crystals with an average size of 21.43 nm. When compared to plant extract and positive controls (AgNO₃ and penicillin), SNPs demonstrated significant bactericidal activity against all the tested bacteria (gram-positive and gram-negative). The most effective bactericidal activity was found against Pseudomonas aeruginosa, with a minimum inhibitory concentration of 1.25 µg/mL. In addition, a dose-dependent antioxidant activity of SNPs was found against the 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical with an average IC50 value of 72.84 µg/mL. The photocatalytic activity of Methylene blue (MB) dye decomposition under sunlight was studied. The results showed that MB degraded by 98 % after 150 min in the sun. Overall, the findings of this study indicate that R. ellipticus biosynthesized SNPs may have bactericidal and photocatalytic effects.     

Radical scavenging activity of sterically hindered catecholate and o-amidophenolate complexes of LSbPh3 type

The radical scavenging effect of the substituted catecholates (1-3, 6) and o-amidophenolates (4, 5) of triphenylantimony(V) in reactions with DPPH^• radical and in a process of oleic acid peroxidation was studied in details. Complexes 1-6 show the high activity in radical scavenging reactions with DPPH^• radical leading to disappearance of radical species. Complexes were demonstrated to be high-efficient inhibitors of chain-radical process of the peroxidation of oleic acid as well as the effective destructors of the formed hydroperoxides. It was found that the effectiveness of complexes studied in the inhibition of the peroxidation of oleic acid depends on the first oxidation potential of complex.